It is well known that amines such as hexamethylenediamine can be produced by the catalytic hydrogenation of nitriles such as adiponitrile in the presence of Raney catalysts.
One such process is described in U.S. Pat. No. 3,821,305, in which hydrogenation is conducted in liquid phase at pressures of from 20-50 atmospheres and temperatures of 60.degree.-100.degree. C. in the presence of finely divided Raney catalyst and an inorganic base. Hydrogen and adiponitrile are fed into a liquid reaction medium consisting of hexamethylenediamine, water, the inorganic base, and the catalyst, in which medium the content of base is maintained in the range of 0.2-12 moles per kilogram of catalyst, while the content of water is maintained in the range of 2-130 moles per mole of the base.
The process discharge stream in the above described process contains both Raney catalyst and the product hexamethylenediamine, from which it is desirable to recover substantially pure hexamethylenediamine by distillation, and to recycle the Raney catalyst.
In order to passify the Raney nickel catalyst so as to prevent decomposition of the product hexamethylenediamine it is known to charge to the product discharge stream an inorganic base. The utilization of this inorganic base to assist in the separation of the product hexamethylenediamine would constitute a significant improvement in the art and is an object of this invention.